A militiaman loyal to Yemen's government inspects the site of a landmine explosion in Yemen's central province of Marib October 13, 2015. (Photo by Reuters/Stringer)

Militiamen loyal to Yemen's government inspect the site of a landmine explosion in Yemen's central province of Marib October 13, 2015. The landmine was set by Houthi militants. (Photo by Reuters/Stringer)

A militiaman loyal to Yemen's government extiguishes the fire on a car destroyed in a landmine explosion in Yemen's central province of Marib October 13, 2015. (Photo by Reuters/Stringer)

A man looks at a graffiti artwork painted by artist Murad Subay in Yemen's war-torn southwestern city of Taiz October 13, 2015. (Photo by Reuters/Stringer)

Houthi militants march during a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

Houthi militants perform during a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

Houthi loyalists shout slogans as they attend a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

A Houthi militant stands guard during a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

Houthi militants perform a dance during a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

Houthi militants perform during a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

A Houthi militant attends a rally commemorating the 52nd anniversary of the start of South Yemen's uprising against British rule, in Sanaa October 14, 2015. (Photo by Khaled Abdullah/Reuters)

A Houthi fighter mans a machine gun on a police truck while securing a road where people demonstrated against the Saudi-led air strikes in Yemen's capital Sanaa October 18, 2015. (Photo by Khaled Abdullah/Reuters)

A man wears images of Yemen's former President Ali Abdullah Saleh during a demonstration against the Saudi-led air strikes outside the United Nations offices in Yemen's capital Sanaa October 18, 2015. (Photo by Khaled Abdullah/Reuters)

A Houthi fighter mans a machine gun on an army patrol truck while securing a road where people demonstrated against the Saudi-led air strikes in Yemen's capital Sanaa October 18, 2015. (Photo by Khaled Abdullah/Reuters)

A Yemeni soldier, pictured through a vehicle's windscreen, which was damaged by a bullet, gestures out of the window, in Marib, Yemen October 15, 2015. Marib is a city that is heavily armed even by the standards of Yemen, where the ready availability of weapons helped start civil war and is now preventing anyone coming out on top. Yemenis often say there are three guns for every person, a boast that has become an urgent concern in a country where the United Nations says the humanitarian situation is "critical". (Photo by Angus McDowall/Reuters)

A soldier loyal to Yemen's government aims a machine gun at a Houthi position in the country's central province of Marib October 19, 2015. (Photo by Reuters/Stringer)

Soldiers loyal to Yemen's government prepare a machine gun as they take position at the frontline of fighting against Houthi fighters the country's central province of Marib October 19, 2015. (Photo by Reuters/Stringer)

A soldier and militiamen loyal to Yemen's government take positions at the frontline of fighting against Houthi fighters the country's central province of Marib October 19, 2015. (Photo by Reuters/Stringer)

Soldiers loyal to Yemen's government ride on the back of a military truck on a road leading to the frontline of fighting against Houthi fighters in the country's central province of Marib October 19, 2015. (Photo by Reuters/Stringer)

Soldiers and militiamen loyal to Yemen's government take position at the frontline of fighting against Houthi fighters the country's central province of Marib October 19, 2015. (Photo by Reuters/Stringer)

A follower of the Shi'ite Houthi movement holds his rifle during a demonstration to commemorate Ashura in Yemen's capital Sanaa October 24, 2015. Ashura, which falls on the 10th day of the Islamic month of Muharram, commemorates the death of Imam Hussein, grandson of Prophet Mohammad, who was killed in the seventh century battle of Kerbala. (Photo by Khaled Abdullah/Reuters)

People stand at the site of a Saudi-led air strike that hit a food storage warehouse in Yemen's capital Sanaa October 25, 2015. (Photo by Khaled Abdullah/Reuters)

Firefighters extinguish a fire at a food storage warehouse hit by a Saudi-led air strike in Yemen's capital Sanaa October 25, 2015. (Photo by Khaled Abdullah/Reuters)

A damaged car is seen at the scene of a suspected suicide attack in Yemen's southern port city of Aden October 26, 2015. A suspected al Qaeda suicide bomber killed two militiamen on Monday at a checkpoint in Aden, already beset by violence, a security source said. (Photo by Reuters/Stringer)

People carry a man at a hospital after he was injured by a shelling during clashes between Houthi militants and pro-government militants in Yemen's southwestern city of Taiz October 26, 2015. (Photo by Reuters/Stringer)

A militant loyal to Yemen's government searches a car at a checkpoint in the country's southern port city of Aden October 19, 2015. (Photo by Reuters/Stringer)

Militants loyal to Yemen's government patrol a road in the country's southern port city of Aden October 19, 2015. (Photo by Reuters/Stringer)

A Houthi militant stands past a destroyed house at the site of Saudi-led air strikes in Yemen's capital Sanaa October 28, 2015. (Photo by Khaled Abdullah/Reuters)

A car covered with rubble is seen at the site of Saudi-led air strikes in Yemen's capital Sanaa October 28, 2015. (Photo by Khaled Abdullah/Reuters)

A man stands at the site of Saudi-led air strikes in Yemen's capital Sanaa October 28, 2015. (Photo by Khaled Abdullah/Reuters)

Houthi militants stand at the site of Saudi-led air strikes in Yemen's capital Sanaa October 28, 2015. (Photo by Khaled Abdullah/Reuters)

A Houthi militant walks at the site of Saudi-led air strikes in Yemen's capital Sanaa October 28, 2015. (Photo by Khaled Abdullah/Reuters)

A boy carries buckets to fill with water from a public tap amid an acute shortage of water, on the outskirts of Sanaa, Yemen, Tuesday, October 13, 2015. The war has taken a heavy toll on Yemen. More than 4,000 people have been killed, and the humanitarian crisis has left the impoverished country on the brink of famine. (Photo by Hani Mohammed/AP Photo)

Smoke rises from a neighborhood following airstrikes allegedly carried out by the Saudi-led coalition, in Sana'a, Yemen, 27 October 2015. According to reports, the Saudi-led coalition intensified airstrikes on several positions in the Houthi-held capital Sana'a and other cities throughout Yemen. (Photo by Yahya Arhab/EPA)

Women stand next a graffiti painted by pro-Houthi activists on the gate of the Saudi embassy in Yemen's capital Sanaa October 21, 2015. (Photo by Khaled Abdullah/Reuters)

Boys hold up jerrycans to represent drinking water during a protest against a Saudi blockade of Yemen's ports, outside the United Nations' offices in Sanaa, Yemen October 19, 2015. U.N.-sponsored talks to end months of fighting in Yemen will convene in Geneva at the end of October, the U.N. special envoy for the issue has announced, urging the parties to try to make the negotiations a success. At least 5,400 people have been killed in the six-month civil war in the poorest country on the Arabian Peninsula, and the United Nations says the humanitarian situation, exacerbated by a Saudi blockade of Yemen's ports, is "critical". (Photo by Khaled Abdullah/Reuters)

A woman and a girl sit next a graffiti painted by pro-Houthi activists on the gate of the Saudi embassy in Yemen's capital Sanaa October 21, 2015. (Photo by Khaled Abdullah/Reuters)

Women stand next a graffiti painted by pro-Houthi activists on the gate of the Saudi embassy in Yemen's capital Sanaa October 21, 2015. The writing reads, "We will kneel only to Allah". (Photo by Khaled Abdullah/Reuters)

A militant loyal to Yemen's government searches a car at a checkpoint in the country's southern port city of Aden October 19, 2015. (Photo by Reuters/Stringer)